Electronic timekeeper



1968 KlYOSHl BANSHO ELECTRONI C TIMEKEEPER Filed Sept. 25, 1965 3 Sheets-Sheet 1 Y INVENTOR.

kvraxwomsys 19.68 I I KIYOSHI BANSHO 3,407,344

ELECTRONIC TIMEKEEPER Filed Sept. 23, 1965 3 Sheets-Sheet 2 .JNVEN'I'OR, Myasb/ Bans/7a BY -""""i a V ATTORNEYS Oct. 22, 1968 KIYOSHI BANSHO 3,407,344

ELECTRONIC TIMEKEEPER' Filed Sept. 23, 1965 3 Sheets-Sheet 5 Flg .11

United States Patent 3,407,344 ELECTRONIC TIMEKEEPER Kiyoshi Bansho, Yokohama-shi, Japan, assignor to Shigeru Kakubari, Tokyo, Japan Filed Sept. 23, 1965, Ser. No. 489,618 Claims priority, application Japan, Sept. 26, 1964, 39/55,173 3 Claims. (Cl. 318-130) ABSTRACT OF THE DISCLOSURE This invention relates to an electronic timekeeper wherein a balance wheel has permanent magnets mounted thereon and a free-running multivibrator associated therewith. A load for the multivibrator is provided by a coil which drives the balance wheel by a mutual action of the flux through the coil and the permanent magnets so that the oscillation period of the multivibrator is controlled by the inherent vibration period of the balance wheel and synchronized therewith.

This invention relates to an electronic timekeeper such as an electronic watch or clock. More particularly, this invention is directed to the provision of an electronic timekeeper which comprises a balance wheel having mounted thereon permanent magnets and a free-running multivibrator having as a load a magnetic coil for driving the balance wheel and in which the balance wheel is driven by a force based upon the mutual action of the flux produced by the impulse fed to the magnetic coil of the free-running multivibrator and that of the permanent magnets mounted on the balance wheel in a manner so that the oscillation period of the free-running multivibrator is controlled by the mechanical inherent vibration period of the balance Wheel and synchronized therewith.

It is one object of this invention to provide an electronic timekeeper having no electrical contacts.

It is another object of this invention to provide an electronic timekeeper which is low in power consumption.

It is another object of this invention to provide an electronic timekeeper which is easy to mass-produce at low cost.

It is another object of this invention to provide a selfstart electronic timekeeper.

It is still another object of this invention to provide a highly precision electronic timekeeper which withstands vibrations or shocks applied thereto from the outside.

Other objects, features and advantages of this invention will appear from the following description taken in conjunction with the accompanying drawings, in which: FIGURE 1 is a side view of an electronic timekeeper of this invention schematically illustrating an example thereof and an electrical system of a free-running multivibrator for use with the electronic timekeeper;

FIGURE 2 is a schematic plan view illustrating the relationship between the mechanical part including a balance wheel and a driving coil in the electronic timekeeper illustrated in FIGURE 1;

FIGURES 3A to 3B, inclusive, are curves for explaining the operation of the electronic timekeeper illustrated in FIGURE 1;

FIGURE 4 illustrates curves for explaining the buildup condition of a pulse induced in the driving coil by the magnets of the balance wheel at the start thereof;

FIGURE 5 is a circuit diagram illustrating another example of the multivibrator which is suitable for reducing the build-up time of the balance wheel;

FIGURE 6 is a circuit diagram illustrating another example of the multivibrator by which the width and amplitude of a pulse produced in the driving coil is auto- 3,407,344 Patented Oct. 22, 1968 matically changed respectively at the start and during the steady-state operation;

FIGURE 7 is a modified form of the circuit illustrated in FIGURE 6;

FIGURES 8 and 9 are further modified forms of the circuit illustrated in FIGURE 6;

FIGURE 10 is a modification of the circuit illustrated in FIGURE 9;

FIGURE 11 is a circuit diagram in which one of the diodes in the circuit illustrated in FIGURE 6 has been removed; and

FIGURE 12 is a circuit diagram illustrating a still further example of the multivibrator usable in this invention.

In FIGURES 1 and 2 reference numeral 1 indicates a balance wheel and 2 its rotary shaft. The rotary shaft 2 is supported between fixed base plates 3 and 4, as illustrated in FIGURE 1. Reference numerals 5a and 5b identify bearing portions for supporting the rotary shaft 2. Reference numeral 6 indicates a spiral hair spring wound about the rotary shaft 2, the inner end of the spring 6 being fixed to the shaft 2 and the outer end being fixed to an arm attached to the fixed base plate 3. Reference numeral 8 identifies a driving screw member mounted on the rotary shaft 2, and 10 designates a wheel mounted on a stationary axis ax and driven by the driving screw member 8. The Wheel 10 is interlocked with the hands of the timekeeper through a gear mechanism including a gear diagrammatically illustrated for the purpose of exemplification. The driving screw member 8 is provided with a helical inclined plane 8a and adapted so that radial fingers 10a of the wheel 10 are sequentially pushed up by the inclined plane 8a in response to the rotation of the rotary shaft 2 to thereby rotate the wheel 10 about the axis ax.

On the rotary shaft 2 there is mounted a sleeve 11 made of a magnetic material in a manner to rotate together with the rotary shaft 2. Both ends of the sleeve 11 have mounted thereon discs 13 and 14, each consisting of semicircular plates respectively formed of magnetic and nonmagnetic materials; On the opposing faces of the discs 13 and 14 there are mounted permanent magnets 15 and 16 of, for example, rectangular parallelepiped shape, spaced apart a distance as identified at 17. These magnets 15 and 16 are placed along the reference line OO of the rest position of the rotary shaft 2, as illustrated in FIGURE 2. The width and length of each magnet in the rotary and radial directions of the disc are selected approximately the same K, as will be described later. The opposing faces of the magnets 15 and 16 are, of course, fiat and constitute magnetic poles N and S respectively.

On the opposing faces of the discs 13 and 14 there are disposed balance weights 19 and 20 spaced a distance, as identified at 18, at the position diametrically opposite to the magnets 15 and 16. Furthermore, a driving coil 21 is disposed between the magnets 15 and 16 on the reference line OO. The driving coil 21 is wound in a manner to form therein a central aperture 22 of an equilateral triangle in cross section and placed so that the bisector of the triangle may lie exactly on the reference line 0-0 and that the peak may stay on the side of the rotary shaft 2. In this case the length of the base side of the aperture 22 and the width of winding of the coil are also selected approximately K which is the width of the magnets 15 and 16. In addition, the both faces of the coil 21 confronting the magnets 15 and 16 are formed flat. Reference numeral 23 identifies a support member of the driving coil 21.

When the rotary shaft 2 is at a standstill, the magnets 15 and 16 cover the central aperture 22. The driving coil 21 is connected to the output terminals 25a and 25b of a free-running multivibrator 24.

The multivibrator 24 consists of, for example, PNP- type transistors V and V of the same conductivity type, as illustrated in FIGURE 1. That is, the emitters of the transistors V and V are connected to the plus side of a DC power source E. The collector of the transistor V is connected to the minus side of the DC power source E through the output terminal 25b, the driving coil 21 and the other output terminal 25a, while the collector of the transistor V is similarly connected to the minus side of the DC power source E through a resistor R The base of the transistor V is also connected to the minus side of the DC power source B through a resistor R on the one hand and through a series circuit of a capacitor C and a resistor R which is parallel to the resistor R on the other hand, while the base of the transistor V is likewise connected to the minus side of the DC power source B through a resistor R n the one hand and through the capacitor C and the driving coil 21 on the other hand. The capacitor C the resistor R and the capacitor C the resistor R respectively constitute elements which determine the time constants T and T for the conduction and non-conduction of the oscillation of the multivibrator 24. In this case, the time constant T determined by the capacitor C and the resistor R and the time constant T by the capacitor C and the resistor R are selected such that T T Meanwhile, the oscillation period T; of the multivibrator 24 equals the sum of the time constants T and T but the oscillation period T,; is selected equal to or slightly greater than one half of the vibration period T under the steady-state operation of the balance wheel 1.

In FIGURE 3A there is illustrated the wave form 25 of the vibration of the balance Wheel 1 with respect to the reference line OO. In FIGURE 3B there is illustrated the oscillating wave form of the output of the multivibrator 24 which is fed to the magnetic coil 21 during free running of the multivibrator 24, namely reference numeral 26 indicating the oscillating wave form produced while the flux of the magnetic coil 21 and that of the magnets and 16 do not cross each other. In this case the reference zero voltage is the potential of the minus side of the power source E. Under such conditions, the multivibrator 24 starts to oscillate and the output is delivered to the magnetic coil 21, so that the upper and lower ends of the magnetic coil 21 are polarized N and S respectively, rotating the discs 13 and 14 and consequently the rotary shaft 2 a little to the left, for example, from the rest position due to the repulsion between the fluxes of the magnetic coil 21 and the magnets 15 and 16. Subsequent to the rotation due to the repulsion, the discs 13 and 14 are then pulled backward to the right by the reaction of the spiral hair spring 6, the center of the magnets 15 and 16 travelling past the reference line 0-0 to the right of the magnetic coil 21. Following this, the discs 13 and 14 are then rotated to the left again in the same manner. In this case, since the pulse is fed to the magnetic coil 21 whenever the magnets 15 and 16 run past the reference line 0-0 to the right and left, the discs 13 and 14 are energized each time to move to the right and left past the reference line 0-0 at angles 0 and 0' thereto respectively.

Now, description will hereinbelow be made in connection with the control of the operation of the multivibrator 24 by the constant-speed vibration or the isochronism of the balance wheel 1. When the balance wheel 1 vibrates, pulses 27 opposite in sense, as illustrated in FIGURE 30, are induced in the driving coil 21 by the fluxes of the magnets 15 and 16 and the polarity of the pulses 27 is reversed when the magnets 15 and 16 pass the reference line OO. With the lapse of time, the induced pulse 27 becomes gradually larger as illustrated by the curves a to c in FIGURE 4, and the transistor V of the multivibrator 24 is triggered at a certain level L through the capacitor C In this manner the multivibrator 24 is controlled by the isochronism of the balance wheel 1 and 4. synchronized therewith. As is apparent from the foregoing, the multivibrator 24v continues to oscillate while being pulled in by the induced pulse 27 based upon the isochronism of the balance wheel 1 and in turn such an oscillator drives the balance wheel 1. By carrying out such an operation repeatedly, the balance wheel is kept in isochronal operation, while the magnetic coil 21 is supplied with output pulses 28 each synchronized with the inherent vibration period T of the balance wheel 1 under the steady state thereof, as illustrated in FIGURE 3D, thereby maintaining the driving of the balance wheel 1.

An example of the numerical values of this invention is as follows: I

K: 5 mm.

Width of the magnets 15 and 16: 2 mm.

T 500 in. sec.

V1 and V2:

C 30 ,uf.

R 750 Kn Coil 21: resistance 30052, 1200 turns, diameter of wire 0.04 mm., thickness of the entire coil in the axial direction of winding 2 mm.

The present invention has been described in connection with the case where the width or the time constant T of the pulse 28 applied to the driving coil 21 is constant. However, it is preferred to slightly increase the width of the pulse 28 from the starting point thereof in order to reduce the build-up time of the balance wheel 1 and to ensure the starting thereof.

FIGURE 5 illustrates a multivibrator circuit for accomplishing this, parts similar to those in FIGURE 1 being identified by the same reference numerals, but no further description will be made thereon for the sake or simplicity. As illustrated in the figure, each one end of resistors R and R is connected to the minus side of the DC power source E through the normally closed contact S of a push-button switch SW and each one end of resistors R and R is connected to the base of each of the transistors V and V while the other ends are connected together to the minus side of the power source B through the normally open contact S of the switch SW. In this case the value of the resistor R is selected smaller than that of the resistor R With such an arrangement, when the contact S is closed by the movable contact S of the switch SW, the width T of the pulse 28 applied to the magnetic coil 21 becomes wider than that T of the pulse 28 shown in FIGURE 3B, as illustrated in FIGURE 3E. Therefore, the build-up time of the balance wheel 1 can be shortened by turning the switch SW to the contact S for an extremely short period of time when starting. Meanwhile, since the pulse width during steady-state operation is narrower than that required at the start, the power consumption from the DC power source E can be reduced. Furthermore, the driving coil 21 is energized by the pulse of narrow width, so that the accuracy of the isochronism of the balance wheel 1 can be enhanced further.

The present invention has been described above in connection with the case where the power consumption is reduced by narrowing the pulse width at the start. It is of course possible, however, that the pulse width and amplitude can automatically be increased at the start and decreased during steady-state operation. FIGURE 6 illustrates a circuit for this purpose, in which a diode D is connected in series to the resistor R in a manner so that the plate of the diode D is connected to the minus side of the DC power source E and the cathode is connected through a diode D to the collector of the transistor V With the use of such a circuit, the amplitude of the vibration of the magnets and 16 is small, and hence the amplitude of the pulse induced in the driving coil 21 is also small. The internal resistance of the diodes D and D is great because a backward bias has been applied to them, and consequently the time constant of the multivibrator 24 is great, including the sum of the resistance of the resistor R and the internal resistance of the diodes and that of the capacitor C As a result the width of the pulse fed to the magnetic coil 21 is great, as illustrated in FIGURE 3E. As will be seen from the voltage-current characteristic of the diode, the internal resistance of the diodes gradually decreases with an increase in the amplitude of the pulse 27 induced in the driving coil 21, reducing the time constant and the pulse width. On the other hand, the energy stored in the capacitor C decreases with a decrease in the pulse Width and the amplitude of the pulse delivered to the driving coil 21 also decreases. Accordingly, only at the start of the operation the driving coil 21 is supplied with a pulse 28' having necessary width and amplitude and thereafter the balance wheel 1 is usually driven by a pulse 28 of smaller width and amplitude, so that power consumption can be reduced. In addition, precision can be enhanced due to the narrow width of the driving pulse.

The circuit illustrated in FIGURE 7 is exactly the same as that in FIGURE 6 except that the internal resistance of the transistor V performs the function of the resistor R which has been omitted.

FIGURE 8 illustrates a modified form of the circuit in which the diode D shown in FIGURE 7 has been left out.

FIGURE 9 illustrates a modification of the circuit shown in FIGURE 6 in which the power source of the resistor R is cut off and the resistor R is connected in series with a diode D;.,, the cathode of which is connected to the collector of the transistor V FIGURE 10 illustrates a circuit in which the diode D in FIGURE 9 has been removed.

FIGURE 11 illustrates a circuit in which in FIGURE 6 has been left out.

The operation of the circuit shown in FIGURES 5 to 11, inclusive, will be apparent from the foregoing description taken in connection with FIGURE 1.

FIGURE 12 is a still further modified form of the multivibrators according to the present invention, in which the multivibrator consists of transistors V and V of the same conductivity type and another transistor V of different conductivity type. That is, the base of the transistor V is connected to the emitter of the transistor V and the collectors of the two transistors are connected together, the emitter of the transistor V being connected to the plus side of the DC power source E and the emitter of the transistor V being connected to the minus side of the power source E. The base of the transistor V is connected through a resistor R to the plus side of the power source E. The collectors of the transistors V and V are connected to the base of the transistor V through a series circuit of a resistor R and a capacitor C and the collector of the transistor V is also connected through a capacitor C to the base of the transistor V and to the plus side of the power source B through a resistor 6, and in addition, the bases of transistors V and V are connected to the minus side of the power source E respectively through a diode D and resistor R The numerical embodiment illustrated in FIGURE 12 is as follows:

Diode D SD102 C3: 1 pf.

R 14.5 Kfl Coil: impedance 3000, 1200 turns, diameter of wire 0.04

mm., width of the axial direction 2 mm.

the diode D While several embodiments of this invention have been described in connection with the case where the balance wheel is employed it is to be understood that the present invention is applicable to electronic clocks employing a pendulum in place of the balance wheel.

It will be apparent that many modifications and variations may be effected without departing from the scope of the novel concepts of this inveniton.

What I claim is:

1. An electronic timekeeper comprising a balance wheel mounted on a rotary shaft, said balance wheel consisting of a sleeve of a magnetic material surrounding the rotary shaft and a pair of opposing discs contiguous to the sleeve, one portion of each disc being magnetic, a pair of permanent magnets mounted on the magnetic portion of each disc with a predetermined distance therebetween, the opposing faces of said pair of permanent magnets being opposite in polarity, a flat driving coil disposed between the pair of discs in the rotary angular range of the pair of permanent magnets, said driving coil being wound in a manner to form therein a central aperture of an equilateral triangle in cross-section and so placed that the peak of said triangle stays on the side of said rotary shaft, the width of the winding of said driving coil around said aperture being selected to be substantially equal to the length of the base of said triangle aperture and the width of said magnets in the direction of the circumference of said disc, and a free-running multivibrator for energizing said driving coil, the oscillation period of said free-running multivibrator being selected equal to or greater than one-half of the vibration period of the balance wheel, the output of the free-running multivibrator being delivered to the driving coil in a manner so that when a driving pulse is applied to the driving coil a magnetic field of the same polarity as the pair of permanent magnets may be established in the faces of the driving coil confronting the pair of permanent magnets, the oscillation period of the free-running multivibrator being controlled by a pulse induced in the driving coil each time the pair of permanent magnets pass the driving coil during the operation of the balance wheel, and the output of the free-running multivibrator produced thereby being applied to the driving coil, thereby repelling the pair of permanent magnets immediately after they have just passed the center of the driving coil.

2. An electronic timekeeper as claimed in claim 1, wherein the free-running multivibrator is provided with means for selecting the time constant in a manner so that the width of the output pulse of the free-running multivibrator at the start thereof may be greater than that of the pulse during the steady-state operation.

3. An electronic timekeeper as claimed in claim 1, wherein the free-running multivibrator is provided with means for automatically selecting the time constant in a manner so that the width of the output pulse of the freerunning multivibrator at the start thereof may be greater than that of the pulse during the steady-state opreation.

References Cited UNITED STATES PATENTS 2,900,606 8/1959 Faulkner 331-113 3,010,078 11/1961 Stefanov 331-113 XR 3,156,857 11/1964 Herr et al. 310-36 XR 3,183,454 5/1965 Streit 331-113 3,200,351 8/1965 Ritchey 331-145 XR 3,238,431 3/1966 Raval 318- 3,064,146 11/1962 Schiininger 310-36 3,095,528 6/1963 Dome 318-132 FOREIGN PATENTS 921,948 3/1963 GreatBritain.

MILTON O. HIRSHFIELD, Primary Examiner. D. F. DUGGAN, Assistant Examiner. 

